It's been a few years and my memory is failing me. Last time I went to the south side of the 3 sisters I came in via devils lake th, but we left going another way. Just wondering if anyone knows the name of the trail just a mile or two (?) to the east? Is it Todd Lake T.H.???

Todd Lake TH is farther east. You can take that trail to Green Lakes, then on to S Sister, but it's much farther.
From Green Lakes TH to Green Lakes it's about 4.3 miles x 1200' gain. From Todd Lake TH to Green Lakes it's about 6.6 miles x 1350' gain.